Check out this never before seen relic that BMW M posted on its Facebook page today. It's a Z3 shoehorned with a V12!
No information was given on the car other than the 3 photos titled "V12 BMW Z3 Prototype," but given the Z3's production run from 1996-2002, we can surmise that the engine seen is the M73 5.4 liter engine from the E38 750i and E38 860Ci coupe from the mid 90's (it also matches visually). The M73 featured 322hp / 361 lb-ft torque. The actual engine that the the Z3 M Roadster and Coupe received was the 3.2L S54 from the E46 M3, good for 321hp / 261 lb-ft torque in Europe and 315hp in North America.
Coincidentally, we got some information on this car back in July during our press drives of the F21 M135i. As we were told, Burkhard Göschel, former BMW board member and then Z3 project leader had the idea to fit a V12 engine in the Z3. As mentioned above, it had about 320hp but it was nothing short of undriveable. With about 70% of weight at the front axle, we were told that the car behaved weirdly -- mildly put.
As maniacal as a V12 Z3 M would have been, this prototype was likely never intended to be anything but a one-off fun project by the M engineers.
This V12 Z3 joins many other BMW prototypes which have never seen the mass production line because they never received approval or were one-off projects, such as the M8 coupe, E92 M3 pickup, E30 M3 pickup, Ur-Roadster, E36 M3 Compact, and E46 M3 Wagon (all of which we witnessed in person at BMW M's Secret Underground Garage